Apparatus for processing wood are well known. Such apparatus is used to convert wood, in the form of raw logs or boards, into wafers, chips or strands for use in various types of composite boards, paper or the like.
Wood processing apparatus generally employ a large rotating disc or ring mounted on a driven shaft. A series of cutting knives are mounted to the disc face or about the inner or outer periphery of the ring, often by bolts. The rotating disc or ring is positioned adjacent to a chamber for holding logs. The disc or ring can be stationary or mounted to a carriage that allows the rotating disc or ring to be slowly advanced through the logs in the chamber. The rotating knives convert the wood into wafers, or strands that are collected and conveyed away below the carriage. The carriage then retracts allowing a new batch of logs to be delivered to the chamber for processing.
In wood processing apparatus of this type, the knives need to be regularly maintained. The knives can be either re-useable or a disposable design. Re-usable knives are generally made from plate steel. Even with scheduled maintenance, knives can be damaged during normal use and it is important to be able to replace the knives as quickly as possible to minimize down time and lost production.
At present, most knives are mounted to the disc or ring by a carrier member and a clamp member. Each knife comprises an elongated blade member having a cutting edge. The carrier member is mounted to the disc or ring, sometimes via a carrier support. The carrier member provides a surface to receive an elongate knife blade. The knife blade is sandwiched between the carrier member and the clamp member and the clamp member is held against the knife blade by a series of locating bolts that extend through the clamping member and into the carrier or carrier support, ring or disc. In this arrangement, the clamping member and carrier member co-operate to act as a third order lever.
To maintain a relatively consistent clamping force, the clamping member is formed as thick and stiff as possible so that the number of locating bolts can be kept to a minimum. At the same time, due to the limited space in many wood processing apparatus, the thickness of the clamping member is limited and clamping bolts must be close together to ensure reliable clamping of the knife blade on the carrier by the clamping member. The more locating bolts that are necessary to locate the clamping member, the greater the time to replace worn or damaged knife blades.